Random Weather generator for Mythic Europe

I am getting ready to run a new Ars Magica game. Weather is critical to things like economic production. And, in Mythic Europe, even more so than in our own world, it affects disease. So I wanted to plan out the broad weather trends over the course of the whole campaign.

Sometimes I have too much time on my hands, so I created this Excel spreadsheet to randomly generate a temperature pattern over 100 years / 400 seasons.

You can download it here:

Version #2 will probably have some kind of precipitation generator; not just temperatures. But this coming weekend is Total Confusion [ TotalCon.com ], so it will probably be some time next week or later...

Feedback welcome.


Cool! Are you generating things for Europe as a whole or for a specific region?

I could see a few follow-ups. First, as you mentioned, precipitation. I could see putting regional variations into it, too. Then, for true pain, daily temperatures and precipitation, probably based off the seasonal average, that would let you describe the weather on any given day, have it be reasonable, and prevent you from having to come up with weather yourself for every day of a long adventure.


I thought most of Europe was like the USA's Pacific Northwest (Washington & Oregon) - there's Summer, there's December & January, and there's 55 (13 C) and raining. 8)

no idea about the Pacific - but there is no "one size fits all" weather in Europe...

The continental weather varies far more than your one suggestion: varying from Spain, Italy, Southern France, Greece with the "Mediterranean" (hot dry or cold dry with sometimes heavy rain)
climate, then across the mountain dominated near-alp regions, and then on either into Scandinavia for a polar-gulf-stream mix or Russia for a central continental weather (long hot summer or long bitter cold winter)
Ireland and Britain and Iceland are heavily influenced by the Atlantic and the warm Gulf Stream ... modern maps show is nearly on the same latitude as Moscow, and is north of Newfoundland;
Madrid level with New York... but the climate of those pairs is completely different across the Atlantic.
Ireland is famous for Nasa's struggle to find cloudless satellite images - "it rains" in Ireland, but almost never freezes.
Britain, especially England is much more variable...

I have known a number of USAns, having stayed in the UK for a few months, reveal that they had discovered why the British always talk about the weather - it's never the same, never constant, ever unpredictable.


While I applaud your enthusiasm, I just don't see me expanding the Excel sheet to do all the things you suggest. If you'd like to take what I've started and add to it, please do so, and please share the result here.

While I like to have a certain amount of stuff prepared ahead of time, I don't feel the need to predetermine a whole year's worth of weather on a daily basis. If it's important to the adventure, I'll figure it out one way or another.

My intent was on a more macro scale. I envision in-game uses like...

  • It was a bitterly cold winter, the worst you can remember. -1 on all aging checks this year.
  • Spring was abnormally warm, and summer was blazing hot. Physicians have to deal with an epidemic of choleric illnesses.
  • Spring was pleasantly warm, just a little above average, and summer was pleasantly mild. Good precipitation in both, but not too much. This leads to an excellent crop yield this year. Your covenant gets extra resources, and you are able to fill the storage cellar with provisions for tougher times.

I'm working on adding the precipitation randomizer to the spreadsheet.

I'm not sure if the previous season's precipitation should have any effect on the next season. It made a bit of sense with temperatures, but my inclination is that each season is totally random. Thoughts from the community?


Good work!

I've read somewhere (quite a reliable source, isn't it? :wink: ) in Western Europe there were famines every 7th or 8th years in average. I think it is better if you attach the -1 aging modifier to famines than the cold winter. And if you use penalty in the bad years you should give a bonus in the good years.

Crop yields depend not only on the temperature but also on the rainfalls. Both of too few or too much rain cause drop of yields.

However I like the idea to introduce some diseases into the game.

Anyway your spreadsheat damaged my Excel thus now if I copy formulas the excel don't recalculate the cells where I inserted them even after a restart.
OK, finally I found where to reactivate.

And the likely reason for causing umbrellas to become part of fashion. :stuck_out_tongue:

Indeed not even close.
Its enough looking at the countries surrounding the Baltic sea to notice that all sides have radically different weather...
And thats just a tiny part in what is still commonly just one or two similar weatherregions.

Heh, even just in France you have quite distinct)climates from region to region (in French). Just compare Provence and Brittany for some extremes.